ecoLincNZ

17 February 2016

A while back we moved our EcoLincnz blog to a new site. We will look at shutting this site down completely at some point in the nearish future. The new site has a bunch more information about ecology at Lincoln University as well as several new articles.

02 December 2015

I've suggested before that The Lord of the Rings by JRR Tolkien is a great way to prepare a young person for a career in biogeography. I would go further and suggest that The Lord of the Rings is a great way to prepare someone for ecology and evolution full stop. I have read the book seven times since my uncle gave me a battered copy in 1979 when I was 12. Growing up in New Zealand meant that the images that I constructed of the LotR landscapes were remarkably similar to that of the movies (although my Shire looked more like the larger rolling hills of South Otago than those of the northern Waikato). I have just read the book again and find it just as enthralling as previously. I also find that as I age, I find different characters and sections of the books more or less compelling than in the past. For example, although younger Adrian enjoyed the travels of Sam and Frodo after the breaking or the fellowship, I used to think it was a little slow. Now I find that I enjoy this part of the books more that the daring-do of what happens to Pippin, Aragorn, Gimli and the rest of the gang. My previous read through was in 2007 and I have since lived through a natural disaster (the Canterbury quakes). Maybe I sympathise more with the personal change and growth that Sam, in particular, goes through in response to the stress and tragedy of his journey. Last time I read the LotR with a biogeographer's eye, noticing the deep history, the landscapes and distributions. This time I read the LotR with more awareness of the ecology, noticing the interactions, the descriptions of habitats, the effects of change, even the climate change effects! One of the things that struck me is that the concept of environment and experience interacting with inherited traits to determine the expression of everything from the plants of the Morgul Vale to how the hobbits put right the Shire when they return. Merry, Pippin, Sam and Frodo are able to rally the Shire on their return to expel Saruman and his occupying forces not because they are genetically superior to other hobbits but because of the experiences that they have been through that have changed their behaviour compared to the rest of the Shire hobbits.

"One does not simply walk into Mordor". Unless you are in New Zealand, and then you can even take your kids.

Take this passage from when Sam and Frodo finally enter Mordor. "And here things still grew, harsh, twisted, bitter, struggling for life. In the glens of the Morgai on the other side of the valley low scrubby trees lurked and clung, coarse grey grass-tussocks fought with the stones, and withered mosses crawled on them; and everywhere great writhing, tangled brambles sprawled. Some had long stabbing thorns, some hooked barbs that rent like knives. The sullen shrivelled leaves of a past year hung on them, grating and rattling in the sad airs, but their maggot-ridden buds were only just opening. Flies, dun or grey, or black, marked like orcs with a red eye-shaped blotch, buzzed and stung; and above the briar-thickets clouds of hungry midges danced and reeled." This reads like a slightly grimmer version of Darwin's 'tangled bank' paragraph from the Origin and similarly it conveys how life adapts to any situation.
A large part of what ecologists and evolutionary biologists do is to look at how populations adapt to changes in the environment. The plants of Mordor have adapted to living in an environment that was once benign to the harshness created by the proximity of a large active volcano and a dark lord. New Zealand, despite what you might see in the LotR movies, is for the most part highly changed from what it once was, although only parts are Mordor-like. Since humans have arrived much of the country has been converted from native vegetation to exotic pasture on which we graze our sheep and dairy cows. The stories of invasive species establishing in New Zealand are numerous, most sharing a similarly grim ending, usually at the cost of native species and the local environment. One story with a twist is that of the native scarab beetle species, Costelytra zealandica, which has colonized the introduced pastures, causing so much grief that it has earned itself the name New Zealand grass grab and a reputation as a pest species. The larvae of Costelytra zealandica feed on the roots of white clover and ryegrass and is the subject of considerable control efforts. Costelytra zealandica is also found on native vegetation which it often shares with a close relative Costelytra brunneum. Costelytra brunneum, however, is seldom found on introduced pasture species. What makes such a difference between close relatives and when do these preferences form?

Some of the variation in Costelytra zealandica

Marie-Caroline Lefort from the Bio-Protection Centre at Lincoln University, along with several colleagues from Lincoln, Plant and Food and Unitec, set out to find the answers to these questions. In a paper published in PeerJ they report the results from a series of experiments. Marie-Caroline (or MC) collected Costelytra zealandica larvae from both native and introduced vegetation, as well as larvae from Costelytra brunneum from native vegetation, and brought them back to the lab. In the first experiment larvae were placed in the centre of a chamber with three exits. The three exits led to either white clover (an introduced host plant), silver tussock (native host plant) or no plant (control) and the choice that the larvae made when exiting the chamber was recorded. In the second experiment the larvae were fed either white clover or silver tussock roots and their weight gain and survival rates over six weeks was recorded. In the choice experiment, larvae from Costelytra zealandica and Costelytra brunneum raised on native plants showed no preference for the types of plants they would move towards. Costelytra zealandica raised on white clover displayed a clear preference for moving towards the clover. In the feeding experiments the larvae from both species raised on native plants showed no difference in survival or weight gain regardless of which roots they were fed. However, Costelytra zealandica raised on clover were 6 times more likely to survive when fed clover roots compared to tussock roots and gained twice as much weight. These results clearly suggest that there are large intra-species differences in Costelytra zealandica and that the early childhood environment that the larva lives in makes a huge difference to how the larva will develop later in life. This flexibility has allowed Costelytra zealandica to expand its host range, increase its evolutionary fitness, and boost its population numbers. Costelytra brunneum on the other hand does not look to have this same flexibility and is mainly restricted to the declining areas of native vegetation. So our invasive native species looks to be a great example of how phenotypic plasticity, allowing childhood experiences to fix how adults will look and behave, can lead to massive advantages. If Sauron had added this variation to his orcs he would have easily conquered Middle Earth. I must keep that in mind next time I read the Lord of the Rings.

07 May 2015

Recently we moved our EcoLincnz blog to a new site. We will look at shutting this site down completely at some point in the nearish future. The new site has a bunch more information about ecology at Lincoln University as well as several new articles.

13 February 2015

Change has been much on my mind recently. With one son moving into Christchurch to continue with university, another moving to Dunedin to start university and only the third at home for a couple more years (he said hopefully), I have been asked repeatedly about what I will do in the medium term. Down size the house? Maybe look at positions elsewhere? Make a lifestyle change? I'm not sure what motivates these comments as I am happy in my nice, large, old house (it would be great to actually be able to use some of the rooms myself, finally). I enjoy living at Lincoln and working at the University. And I like being an evolutionary biologist. However, on Darwin Day 2015, let me consider my options. If I was to look for another evolutionary biologist position (especially one that focused on biogeography or coevolution) my options would be fairly limited. Within New Zealand there are about seven other similar positions at universities, maybe about the same again in Crown Research Institutes.

Rangitira

In the 20 years that I have been at Lincoln I can remember evolutionary biologist jobs coming up about three times. So it would be very difficult to move within New Zealand. Should I want to go overseas then there are definitely more jobs, but not a whole lot more (and there is a lot of competition!). So I am reasonably tied to Lincoln. Why? Because I am so specialised. To do my job I need a research environment, access to postgraduate students, funding, an organisation that values evolution research and so on. Specialisation, while allowing me to be successful in what I do, has effectively limited my dispersal ability (providing I want to stay being an active evolutionary biologist).

Similar thoughts abound in biology about specialisation. The idea is that specialisation allows a species to do really well as it efficiently utilises a niche but, come a crisis like climate change or a new predator, specialisation will hinder fast adaptation for change for the species and generalists will win out in these situations. So specialists are successful during stable periods but generalists do better in unstable periods, or so theory suggests. It is also thought that species can become so specialised that there is no way back to being a generalist. This has been summarised as Dollo's Law which states that evolution is not reversible. While we know of many examples where evolution does reverse (descendent species becoming more like distant ancestors rather than recent ancestors) specialisation does seem to make such reversals more difficult. For example, parasitism is often portrayed as a dead-end in evolution. Many parasites lose all sorts of traits, such as limbs, complex digestive systems, sense organs and so on, mostly because they live in their food. Once you have lost or substantially changed these traits then it is incredibly difficult to return to a nonparasitic way of life (but not impossible as Rob Cruickshank and I showed for mites a few years ago).

Two coxella weevils getting acquainted.

For most species this issue, while interesting to evolutionary biologists, is not a real day-to-day concern. However, for threatened species this problem of specialisation can influence the likely fate of the species. If a species is too specialised then it may be too difficult to find a solution that will allow the species to be conserved. If you need to live in a certain type of habitat, say peat wetland, and this habitat is limited or disappearing, then you have a problem. If you need to eat a certain type of food, say a particular type of honey dew, and the insect that produces the dew is limited or disappearing, then you have a problem. Emily Fountain, with Jagoba Malumbres-Olarte, Rob Cruickshank and myself, have investigated this problem in a threatened weevil species, the coxella weevil (Hadramphus spinipennis). This weevil species is found in the Chatham Island group, an isolated archipelago 800km east of mainland New Zealand. The coxella weevil is now found on two small islands, Mangere and Rangatira, which are 15 kms apart. The weevil lives on, and eats, one plant species, Dieffenbach’s speargrass (Aciphylla dieffenbachii). The coxella weevil was once found over the whole Chatham archipelago but now persists on these two small islands in small clumps of speargrass. The speargrass is extremely patchy and this is not helped by the weevils who will graze out patches of a plant before moving to a new patch. Both islands were once over-run with livestock (which found the speargrass tasty) and since their removal there has been much planting of native forest trees and natural regeneration, which removes suitable habitat for the speargrass to grow in. So the coxella fate seems tied to the plant that they have specialised on which must make them susceptable to extinction.

Rangitira with Pitt Island in the distance

Emily and Jagoba surveyed the populations of coxella weevil and speargrass on Mangere and Rangitira. She collected a tarsus off the end of one leg from each weevil that she found and was able to extract DNA from these individuals. Emily, in a paper published in PeerJ, found that there was a small difference between the weevil populations on each island, what you might expect if they had been isolated for a relatively short amount of time (around 1000 years). Despite the differences, this indicates that even these specialised weevils can disperse over water, at least occasionally. There was a lack of genetic diversity which suggests that the weevil populations have been through a bottleneck. There was even some evidence that the coxella weevil is sometimes found on other plant species, although whether they are foraging or not could not be determined. On the upside, populations of weevils and speargrass have not declined as a result of the reforestation efforts at this point. So is specialisation a problem for the survival of the coxella weevil? It's fair to say that specialisation on speargrass will not help with conservation efforts, but so far it does not appear to have consigned this species to extinction just yet. After all, it's still easier for a coxella weevil to find a new speargrass plant than it is for an evolutionary biologist to find an evolutionary biology job!

03 February 2015

Morgan Shields was a third year undergraduate student when he found a new species of weta as part of his field ecology course. Morgan tells us how this came about.

A brand new weta species!

Finding a new species is a dream of most budding biologists.
However, for many this never becomes a reality. I was lucky enough to live this
dream during the 2014 ECOL310 Field Ecology course at Lincoln University, when
I collected a highly divergent species of cave weta (Rhaphidophoridae) during
my research project. A highly divergent species is one that is identified as
likely new species but has not been confirmed. It was a pretty sweet feeling
that, as an undergraduate student, I had found something that no else had
likely ever documented before. My excitement was magnified when the find was
celebrated by lecturers in the Ecology department who had taught me for the
last three years.

Our intrepid student hard at work.

However, my buzz soon wore off as reality sunk in.Although the specimens had been identified as
a likely new species of the genus Pleioplectron by entomologists Peter Johns
and Marie McDonald, who specialise in weta, this could not be confirmed without
detailed phylogenetic and morphological studies. And these are only the first
steps to formally recognising a new species; one must then study many specimens
to determine the natural variation within the species and create a formal
description with assigned voucher specimens to show how this weta differs from
all others. This description then has to be published in a taxonomic journal,
having gone through a rigorous peer-review process from experts in the field.
Only then is the species named, which is a privilege for any entomologist. It
is currently unclear who will undertake this journey but perhaps it could be a
pet project of mine. Having realised the lengths required to formally describe
new species, I have come to the conclusion that in many circumstances, such as
my project, it is simpler to find an already known species.﻿﻿

A pitfall trap in the forest at Boyle River.

The cave weta were collected during my field
ecology project at Boyle River, near the Lewis Pass in the Southern Alps of New
Zealand, which examined how invertebrate community composition differs between
native beech and kanuka habitats. This information could then contribute to
invertebrate conservation. Pitfall traps, which are essentially plastic cups
with a preservative inside, were used to catch the weta and other invertebrates
which were identified to recognisable taxonomic units (RTUs). These RTUs are
then looked at by experts and my highly divergent cave weta species was later
determined as a likely new species. Reflecting on this adventure, the field
ecology course provided this opportunity to find some of New Zealand’s hidden
wonders and apply the skills that I had learnt in my degree on a real research
project, in a spectacular part of the Southern Alps and supported by hands-on
lecturers. This was one of the best courses I have taken and I would recommend
it to anyone who wants to get out into the bush to do some real hands-on
ecology.

14 January 2015

This year we are likely to develop a problem with leftovers at home. For the last few years leftovers have had a very short life in our fridge. You see we have had three teenage boys (and assorted teenage friends) around the house and it really is true about what they say about teens. They eat! So leftovers are usually consumed within a day or two as a snack between snacks. However, this year eldest son is moving out to flat in Christchurch while he continues with his engineering degree and second son is heading to university in Dunedin. That will leave mum, dad and youngest at home. So leftovers may well sit and increasingly take up space! Of course our food bill should go way down and the mean consumption per individual should go down as well. This does underline the variability that occurs when you measure foraging (finding and eating food) across life stages, seasons and so on. Another source of variation is in the social aspect of eating. Foraging behaviour can change in groups as well, whether from missing out through competition, such as when your teen uses the last of the milk so that you have none for your cereal, or trying food you wouldn't normally eat, such as last evening when we were at a Chinese restuarant and I tried some chilli jellyfish that a friend had ordered.

A New Zealand dragonfly Uropetala adult. What hungry teens they must have!

Complications in understanding foraging also apply to other organisms as well. While getting a good handle on foraging is always useful, it becomes very important in biocontrol situations. Often a biocontrol solution to dealing with a pest species is to introduce or enhance another species that will eat the pest. Perhaps the pest is an invasive species that has left its usual predators behind, or maybe it is a native species whose natural predators have declined to a point at which they are unable to control pest numbers. Understanding the foraging of predators on the target pest species becomes of prime importance.

One group of pests that are globally in need of control are the mosquitoes. Well over one million human deaths are recorded each year as a direct result of diseases carried by mosquitoes. Insecticides can only do so much and one important strategy is to encourage natural predators that can keep local mosquito populations in check. One type of predator that can make a difference are species from the order Odonata (the dragonflies and damselflies). These predators can munch their way through lots of mosquito larvae, or so previous research has suggested. However, these previous studies have looked at foraging rates in later naiad stages. This is like basing foraging rates in humans on observations of teens, and starving teens at that. Also, previous experiments were done with one Odonata species and one mosquito species. In nature, in addition to different life stages of the predator and prey in a local habitat, there are usually several different species of Odonata predators and mosquitoes.

Another Uropetala

In order to assess what foraging rates are like in more complex (and more realistic) conditions, Robbie Weterings, Chanin Umponstira and Hannah Buckley looked at dragonflies, damselflies and mosquito communities in Thailand. Odonata naiads were collected from canals around Mueang Kamphaeng Phet and sorted into dragonfly and damselfly groups (there were seven species in all). Mosquito larvae were collected from roof drains and water storage containers (there were two species). Containers were filled with water and a water plant was placed in them as well to provide some habitat complexity. One to five dragonflies or damselflies naiads of various ages from the various species were added to the container and finally 10 to 50 mosquito larvae from both species were introduced. Predation rates were then measured. In a paper in the Journal of Asia-Pacific Entomology the authors present the results of the experiment. Dragonflies consumed about 6 mosquito larvae per day and damselflies around 5. This was an order of magnitude lower that what had been recorded for earlier experiments (which had used the equivalent of starving teens). Rate of predation was related to how many prey were around (more prey more eating) and how many rival predators there were (more rivals, more competition). So measuring a cross section of your community in a complex habitat does make a difference when looking at how effective predators are. The good news is that even with these lower rates of predation for dragonflies and damselflies than previously found, if habitats have a healthy Odonata community then this should still keep mosquito numbers under reasonable control. Something to ponder as I gaze at a fridge-full of leftovers later in the year!

Ecology & Evolution @ Lincoln

ecoLincNZ is written by the staff and students of Lincoln University. Research in ecology, evolution, conservation, and environmental management is spread across several departments and institutions on campus, including the Department of Ecology, the Bio-Protection Research Centre, and the Environment, Society, and Design Faculty. We specialise in research and teaching in the likes of entomology, plant pathology & crop protection, ecology, conservation & wildlife management, evolution, molecular genetics and biodiversity. We offer Bachelor of Science (B.Sc.) undergraduate degrees majoring in Conservation & Ecology and Bioprotection & Biosecurity, as well as a Bachelors in Environmental Management and Planning, and have a keen team of research staff, postdocs, and postgraduate students (M.Sc. and Ph.D.)

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